Question

A vertical lamp-post 6 m height stands at a distance of 2 m from a wall, 4 m high. A 1 -5 m tall man starts to walk away from the wall on the other side of the wall in line with the lamp-post. The maximum distance to which the man can walk, remains in the shadow is

• A. $\frac {5} {2} m$
• B. $\frac {3} {2} m$
• C. 4 m
• D. none of these.

Answer 1

Answer: (A)

$\frac {5} {2} m$

Answer 2

BD is the reqd. distance From similar triangles $\frac{6}{4} = \frac{QR}{BR} \, i.e., \, \frac{3}{2} = \frac{2 + BR}{BR} \Rightarrow BR = 4$ $\frac{4}{3/2} = \frac{4}{DR} \, \therefore \, DR = \frac{3}{2}$ $\therefore \, BD = BR - DR = 4 - \frac{3}{2} = \frac{5}{2}$